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A Velocity Dealiasing Scheme for Synthetic C-Band Data from China’s New Generation Weather Radar System (CINRAD)

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  • 1 Center of Data Assimilation for Research and Application, Nanjing University of Information Science and Technology, Nanjing, China
  • | 2 Center of Data Assimilation for Research and Application, Nanjing University of Information Science and Technology, Nanjing, China, and Department of Earth, Ocean and Atmospheric Sciences, The Florida State University, Tallahassee, Florida
  • | 3 Department of Earth, Ocean and Atmospheric Sciences, The Florida State University, Tallahassee, Florida
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Abstract

A velocity dealiasing algorithm is developed for C-band (5-cm wavelength) Doppler radars. With the shorter wavelength, C-band radars operating in a single PRF mode have a Nyquist interval about one-half that of S-band radars. As a proxy for C-band radar data, S-band Doppler data were sampled to produce radial velocity patterns as they would have been observed by a C-band Doppler radar. This algorithm includes six modules, some of which are modifications to previously existing methods. The modules (i) remove weak signals and determine the reference radials and dealias the radial wind field with a continuity constraint, (ii) perform a bulk continuity check, (iii) perform a “box” check to provide local consistency, (iv) perform a linear consistency fit in the radial direction, (v) provide quadratic least squares fit in the azimuthal direction, and (vi) perform quadratic least squares fit for elevation angle above 6.0° only for data from typhoons. The proposed dealiasing algorithm was tested on data from four typhoons and one squall line observed in China. When compared to the dealiasing results of the synthetic C-band data by the existing Next Generation Weather Radar (NEXRAD) algorithm, it was consistently better, particularly with smaller Nyquist cointervals. The algorithm correctly dealiased 91.56% of the aliased radial velocity data in all test cases.

Corresponding author address: Dr. X. Zou, Department of Earth, Ocean and Atmospheric Science, The Florida State University, Tallahassee, FL 32306-4520. E-mail: xzou@fsu.edu

Abstract

A velocity dealiasing algorithm is developed for C-band (5-cm wavelength) Doppler radars. With the shorter wavelength, C-band radars operating in a single PRF mode have a Nyquist interval about one-half that of S-band radars. As a proxy for C-band radar data, S-band Doppler data were sampled to produce radial velocity patterns as they would have been observed by a C-band Doppler radar. This algorithm includes six modules, some of which are modifications to previously existing methods. The modules (i) remove weak signals and determine the reference radials and dealias the radial wind field with a continuity constraint, (ii) perform a bulk continuity check, (iii) perform a “box” check to provide local consistency, (iv) perform a linear consistency fit in the radial direction, (v) provide quadratic least squares fit in the azimuthal direction, and (vi) perform quadratic least squares fit for elevation angle above 6.0° only for data from typhoons. The proposed dealiasing algorithm was tested on data from four typhoons and one squall line observed in China. When compared to the dealiasing results of the synthetic C-band data by the existing Next Generation Weather Radar (NEXRAD) algorithm, it was consistently better, particularly with smaller Nyquist cointervals. The algorithm correctly dealiased 91.56% of the aliased radial velocity data in all test cases.

Corresponding author address: Dr. X. Zou, Department of Earth, Ocean and Atmospheric Science, The Florida State University, Tallahassee, FL 32306-4520. E-mail: xzou@fsu.edu
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